The two predominant topologies, known in prior art, and used for class-D amplifiers are the full-bridge- and the half-bridge topology.
For low cost consumer products the half-bridge topology has a distinct advantage over the full-bridge since only half the number of power switches, drivers and output inductors is needed. Even though the voltage rating of the power switches is doubled in the half-bridge topology, there is still a manufacturing and cost benefit of the reduction. Since the speaker output terminals are referenced to ground, overload protection and output sensing becomes easier compared to the full-bridge topology.
The drawback of the half-bridge class-D topology is the need for a dual rail supply and the fact that this topology will pump current back to the opposite supply rail from where the power is being drained.
Document WO 2010/022220 discloses one approach to supply pump cancelling. According to this solution, a logic module detects where the highest voltage is, and drives one of two switches to transfer energy.
In an earlier application from the applicant (US 2009/0102295) an efficient solution to the rail pumping problem has been disclosed. By that invention the advantages using a single-ended class D-amplifier in consumer products has been obtained.